Writing instrument cap



FIG. 1 is a top left perspective view of a writing instrument cap showing my new design;

FIG. 2 is a front elevational view;

FIG. 3 is a right side elevational view;

FIG. 4 is a rear elevational view;

FIG. 5 is a top plan view; and,

FIG. 6 is a bottom plan view thereof.

The writing instrument barrel depicted by means of broken lines in FIG. 1 is shown for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a writing instrument cap, as shown and described. 